This study was performed to evaluate enhanced effect of fermented Galgeun tang (GGT) and Ssanghwa tang (SHT) on the anti-platelet aggregation. Platelet aggregation assay was performed In vitro using human platelet rich plasma(PRP) and In vivo using SD-rat plasma by platelet aggregometer. Pharmacodynamic parameters, $E_{max}$ and $EC_{50}$, were calculated using Winnolin. SD-rats administered 1 g/kg of oriental medicine every 12 hr for 8 days. Platelet aggregation was measured by optical method with collagen inducer (4 ${mu}g$/ml). In In vitro anti-platelet study, $EC_{50}$ of GGT-A was lower than that of GGT-con about 79.13 ${mu}g$/ml. And $EC_{50}$ of SHT-A and SHT-B was lower than that of SHT-con about 122.73 and 110.15 ${mu}g$/ml, respectively. It is assumed that fermented GGT and SHT were more effective than original medicine. In multiple administration study, anti-platelet effect was significantly increased both GGT and SHT. Fermented GGT and SHT were more effective than original herbal medicine on anti-platelet aggregation.